a lot of law enforcement involved in that. to assist that we have suspended all service on the m.b.t.a., our public transit service, and this will continue until we think it's safe to open all or some of that. we're asking people to shelter in place-- in other words to stay indoors with their doors locked and not to open the door for anyone other than a properly identified law enforcement officer. and that applies here in watertown where we are right now. id walham, newton, belmont and, at this point, all of boston. all of boston. this is a serious situation. we're taking it seriously. we're asking the public to take it seriously as well and to assist law enforcement by following these simple instructions. we've got every asset that we can possibly muster on the ground right now. they are doing a terrific job and working in concert with each other but we are going to need the public to help us help them stay safe. >> reporter: in washington, the president convened a briefing in the white house situation room with almost a doze